This invention relates to electro-optical systems and, particularly, to optical ranging systems for preventing the collision of a vehicle so equipped with a noncooperating vehicle or other roadway object.
Collision avoidance schemes are well known and include systems utilizing radar and radio frequency, laser and optical techniques. A goal of each of these systems is to supplement operator (driver) control during such times when operator inadvertence causes the vehicle to approach an obstacle, or another vehicle, at an excessive rate of speed making safe stopping difficult or impossible.
Collision avoidance systems often require the active cooperation of the obstacle being avoided, that is, the obstacle often must be capable of receiving transmitted energy. Consequently, at a minimum, an antenna or reflector must be mounted to the obstacle. Often the obstacle, a second vehicle, is required to generate an independent signal therein requiring a second vehicle to contain a transmitter. This requires specific frequency assignments of the electro-magnetic radiation from one or both vehicles. In addition, care must be taken to avoid radiofrequency interference or prevent inadvertent activation of other vehicle systems such as adaptive braking systems.
It is a broad object of the present invention to supplement driver awareness of a dangerous situation, to help avoid accidents.
It is an object of the present invention to provide a collision avoidance system which literally watches the road scene ahead of the equipped vehicle independent of driver cooperation.
It is a further object of the invention to determine distance without the cooperation of the obstacle, object or vehicle to be avoided.
It is a still further object to determine the distance and closing rate between a vehicle and an object by measuring the rate of growth of the image and generating a collision avoidance signal when the rate of closure and distance between the vehicle indicate an impending dangerous condition.
These and other objects and purposes of the invention will be clear from the following detailed description of the invention.
Referring first to the bar chart shown on FIG. 7, which illustrates the total stopping distance as a function of vehicle speed. This chart gives an estimated number of feet your car will travel on dry and wet pavement from the time a typical driver perceives danger until he can bring his car to a stop. The stopping distance is segmented into two parts; the distance travelled before the driver reacts to a preceived danger and the distance travelled after the brakes are applied.
The perception/reaction distance 700 is based upon an average of 1.75 seconds between seeing the danger and deciding to stop and another 0.75 seconds to push the brake pedal to the floor. Thus, safe driving would necessitate having a time-space cushion of 2.50 seconds and its corresponding distance between the equipped vehicle and the roadway obstacle. Thus, at a minimum, a system which automatically provides this time-space cushion and supplements driver perception will permit the driver to respond or associated collision avoidance mechanisms to be initiated in a timely manner.
A system is disclosed to avoid a collision between an equipped vehicle and an obstacle reflecting optical radiation.
The invention is applicable to general highway driving conditions, however, the equipped vehicle need not be a car or truck but can be any other type of vehicle such as a people mover traversing within a dedicated guideway.
A particular advantage of this optical approach is that it is amenable to a variety of data processing strategies to overcome spurious responses. The present invention supplements driver awareness permitting automatic perception and mechanized comprehension of potentially dangerous driving situations. By the very optical nature of the collision avoidance system, it receives the cues that a driver should have seen. In addition, the optical nature of the invention readily permits the collision avoidance system to be integrated into visual surveillance systems of driverless vehicles.
The collision avoidance system comprises an electro-optical image sensor such as a charger transfer device and an image processor. An object such as another vehicle lying in the projected path of the equipped vehicle will have its image projected upon the electro-optical sensor. An image processor responds to the size of the projected image and its rate or rates of change, and the velocity of the equipped vehicle and determines the range of the object. If the object is too close for a given relative closure speed (r) range (r), and closure speed range ratio (i.e. r/r) between the object and the equipped vehicle, a collision avoidance signal is generated. The avoidance signal may activate an alarm alerting the operator of the pending emergency. Alternatively, the avoidance signal could be used to activate a collision avoidance system such as a speed control or braking mechanism.
In an alternate embodiment of the invention the lateral motion of objects with respect to the pathway of the equipped vehicle is also computed and a collision avoidance signal generated for the laterally approaching obstacle or vehicle.